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CVE-2021-22901

Published: 26 May 2021

curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client. When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL, it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (like with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established on that connection and then the function will access a memory buffer that might be freed. When using that memory, libcurl might even call a function pointer in the object, making it possible for a remote code execution if the server could somehow manage to get crafted memory content into the correct place in memory.

Notes

AuthorNote
mdeslaur
since 7.75.0 only

Priority

Medium

Cvss 3 Severity Score

8.1

Score breakdown

Status

Package Release Status
curl
Launchpad, Ubuntu, Debian
bionic Not vulnerable
(7.58.0-2ubuntu3.13)
focal Not vulnerable
(7.68.0-1ubuntu2.5)
groovy Not vulnerable
(7.68.0-1ubuntu4.3)
hirsute Not vulnerable
(7.74.0-1ubuntu2)
jammy Not vulnerable
(7.74.0-1.2ubuntu1)
trusty Not vulnerable

upstream
Released (7.77.0)
xenial Not vulnerable

impish Not vulnerable
(7.74.0-1.2ubuntu1)

Severity score breakdown

Parameter Value
Base score 8.1
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H